The present invention relates to novel materials with electrochemical properties, in particular paste-like masses, layers produced from these masses that are self-supporting or that are placed on a substrate and that can be flexible, and composite layers produced therefrom that can be used as primary batteries, accumulators, low-temperature fuel cells, solar cells, or the like.
Since the beginning of the 1970's there have been attempts to produce electrochemical elements such as accumulators or the like in the form of thin layers. The goal has been to obtain composite films that have particularly good charging and discharging properties due to an extremely high contact area between the individual electrochemical components, such as electrodes and electrolytes, relative to the volume of active electrochemical material used. In special circumstances such composite films are also required to have high flexibility so that they can be rolled up or made to conform to another desired shape.
In the past, attempts to produce such electrode materials have begun with solid or viscous liquid Teflon, which is mixed with a certain percentage of carbon and the actual electrode material and is then pressed or sprayed onto suitable contact electrodes. However, this results in layers that have insufficient flexibility. In addition, it has been suggested that electrode layers be produced that are manufactured with PVC and tetrahydrofurane or another polymer dissolved in a solvent and that the solvent subsequently be extracted therefrom. However, the conductivity of products produced in this manner is not favorable.
Producing a layer that can function in an appropriate electrochemical composite as an electrolyte presents particular problems. U.S. Pat. No. 5,456,000 describes rechargeable battery cells that are produced by laminating electrode and electrolyte cells. Used for the positive electrode is a film or membrane that is produced separately from LiMn2O4 powder in a matrix made of a polymer/copolymer and is then dried. The negative electrode comprises a dried coating of a pulverized carbon dispersion in a matrix of a polymer/copolymer. An electrolyte/separator membrane is arranged between the electrode layers. For this purpose a poly(vinylidene fluoride)-hexafluoropropylene copolymer is converted with an organic plasticizer such as propylene carbonate or ethylene carbonate. A film is produced from these components and then the plasticizer is extracted from the layer. The battery cell is maintained in this “inactive” condition until it is to be used. In order to activate it, it is immersed in a suitable electrolyte solution, whereby the cavities formed by extracting the plasticizer are filled with the liquid electrolytes. The battery is then ready for use.
Such a construct is disadvantageous in that the battery must be activated shortly prior to the point in time at which it is to be used. This is not acceptable in most cases.
The object of the present invention is to provide paste-like masses that already contain the appropriate conductor (ion or mixed conductor, especially the electrolytes or at least one of the electrodes) in liquid form and that are suitable for producing electrochemically activatable layers with such a liquid conductor in corresponding electrochemical elements that can be employed immediately. These elements should be suitable for a broad spectrum of products such as primary batteries, rechargeable batteries (accumulators), low-temperature fuel cells, solar cells, electrochemical sensors, or the like, that can have a layer form, in particular the form of a film laminate, that have very good conductive properties and, if required, high flexibility, and that furthermore cannot leak out and that therefore do not necessarily have to be arranged in housings, in particular in sealing housings.